Method of making semipyrophoric iron and the product obtained thereby



Patented July '16, .1940

UNITED STATES PATENT OFFICE Alfred Schmid, Berlin-Dahlem, Germany,assignor to Oswald F. Wyss, Zurich, Switzerland No Drawing.

Original application August 2'), 1932, Serial No. 630,702.

Divided and this application August 11, 1937, Serial No. 158,593. InGermany August 28, 1931 2 Claims. (01. 15-33) a This application is adivisional of my copending; U. S. application, Serial No. 630,702, filedAugust 27, 1932 now U. S. Patent 2,096,009, dated October 19, 1937.

5 This invention relates to a method of producing semipyrophoric ironand the product obtained thereby, and has for its main object to providea safety ignition mixture, the combustion of which takes place withoutflame and without .the production of poisonous or bad smelling gases orof both.

The known ignition mixtures used for starting combustion processesgenerally consist of the following constituents:

(a) Easily decomposable substances yielding oxygen by decomposition,such as chlorates, nitrates, chromates, peroxides, and the like.

, (b) Substances easily inflammable at lowtemperatures such asphosphorus, sulfur, carbon or compounds of the same.

(0) Additions of hard and chemically inert substances increasingfriction, such as quartz, clay, pumice stone and the like.

(d) Binding agents such as glue, starch, gum

arabic and the like.

(e) Substances preventing an explosive comibg listion such as zincoxide, iron oxide and the e. Due to the presence of the substancesmentioned under b, all known ignition mixtures are combusted with flamesand evolution of poisonous or evil smelling gases or of both. Their useis therefore impossible in all those cases, where open flames or theevolution of gases are dangerous or noxious. The present inventionprovides for a safety ignition mixture which may easily be ignited onthe usual friction surfaces for mety matches and are combusted withoutflame and without 40 evolution of noxious or evil smelling gases.Selfignition of the new ignition mixtures is impossible. The newignition mixtures are especially suitable as igniting-heads for cigars,cigarettes and matches, which are safely and efllciently 45 lighted bymore friction on one of the usual friction surfaces for matches, whichsurfaces are preferably arranged on or in the packages for the cigars,cigarettes or matches.

According to the invention the phosphorus, 5o sulfur or the like presentin the known ignition mixtures is replaced by metals with a sufficientlylow ignition temperature such as magnesium, aluminium, zinc. iron,cobalt and the like, which on combustion do not furnish volatilecombustion 55 products but solid oxides in form of a powder.

The main feature of the new ignition mixtures is the absence ofphosphorus, sulfur, carbon or their compounds, the inflammability of themixture being solely due to the combination of oxygen yieldingsubstances with easily ignltable 5 metals. For many purposes ordinarymetals would yield ignition mixtures, the ignition of which would be toodiflicult for the purpose in question. The invention provides for meansto bring these 10 metals into a, form, in which their rapid oxidation orcombustion is facilitated.

It is known, that certain metals such as iron or cobalt may be obtainedin the pyrophoric form by reducing at relatively low temperatures suitisable compounds of these metals with streaming hydrogen. These pyrophoricmetals are, however, ignited and combusted by contact with oxygen or airat room temperature. This pyrophoric form of metals is not suitable, forthe purpose of 20 the invention and the invention therefore has for itsfurther object, to provide for a method, which enables the manufactureof metals in such a form, that they may be ignited with air attemperatures above atmospheric temperature, 25 preferably above 50 C..but below 300 C. I have named this form of metals semipyrophoric," whichis an intermediate form between pyrophoric and normal form. This methodfor making semipyrophoric metals consists in a reduc- 30 tion of metalcompounds suitable for the manufacture of pyrophoric metals under suchmodified reducing conditions that neither the pyrophoric nor the normalform is obtained or. in treatment of pyrophoric metals which makes themmore diflicul-tly ignitable. The reduction of the metal compounds may becarried out by thermal decomposition in presence of inert gases or bytreatment with hydrogen at raised temperatures.

A metal is "semipyrophoric when, on the one hand, it is notself-ignitable by mere contact with air and, on the other hand. is notso dimcultly ignitable as in the normal state but can be brought into astate of ignition by friction on a friction surface. Or, in other words,a metal is semipyrophoric" when its ignition temperature (1) Is not solow that it ignites by contact with air at room temperature;

(211s not so high that it does not ignite by friction on a speciallyprepared friction surface; so

(3) But is of such a nature that mere friction on a specially preparedfriction surface is mfflcient for igniting the metal.

Temperature and duration of these treatments must be kept within limits,outside of which a pyrophoric or vnormal -metals are obtained. Startingmaterials for the method according to the invention are inorganic ororganic metal compounds such as'oxides, nitrates, carbonates, sulfates,oxalates, tartrates or the like.

- Pyrophoric metals may be converted into semipyrophoric metals by ashorter or longer heat 'treatment in the presence of inert gases, suchas nitrogen, hydrogen and the like.

For the manufacture of semipyrophoric metals theduration of thetreatment is a function of the temperature. Moreover temperature andduration of the treatment are difierent for different metals, gases andpressures employed. It is therefore not possible to give general datafor temperature and duration of the treatment,-but the followingexamples may lead the expert in finding the conditions for makingsemipyrophoric metals other than iron or semipyrophoric iron from otherstarting materials or by a modified method.

Example I 10 gr. of ferrous oxalate are heated to about 400 C. instreaming hydrogen, which has been .dried by passing it throughconcentrated sulfuric acid before entering the reaction zone and whichpasses this zone at a moderate rate corresponding to about two gasbubbles leaving the sulfuric acid per second.

When the amount of gases leaving the reaction zone decreases, which isthe case after about one hour, the reaction is finished. The heating isstopped and a rapid cooling is eflected by passing hydrogen through thereaction zone. when room temperature has been reached a black powder isobtained not ignitable by contact with air, at room temperature, butignitable, when contacting it with air at about 180 C.

Etnample II I 28 parts of the semipyrophoric iron produced in the mannerdescribed are mixed with 25 parts of potassium chlorate, 1 part ofpyrolusite and 18 parts of powdered burnt clay. The mixture is powderedand mixed while stirring with parts of a 4% solution of collodion involatile organic solvents, some ether and alcohol being added to thepappy mixture it necessary. The mixture is placed on the top of a cigaror cigarette in any convenient manner, thus obtaining a firmly adheringignition head on the article after evaporation of the volatile solventin the air.

The igniting mixture described above may contain other substances, suchas fillers and the like, or may be combined with other pyrotechnicmixtures. It may be arranged on any inflammable'carrier and thus serveto light any combustible substance.

The solution of collodion employed as binding agent in the above examplemay be replaced by solution of other binders, such as acetyl celluloseand the like, in volatile organic solvents, such as alcohol, ether,acetone, amyl acetate and the like. Also aqueous solutions of glue,starch, gum arabic and the like may be employed, although binderscontaining volatile organic solvents are preferred, as thesolidification of the ignition mixtures on their carriers isaccelerated, when the binder contains volatile liquids as solvent. Theamount of binder used is kept as low as possible and preferably suchbinders are employed, which are easily and completely combusted withoutthe evolution of noxious or bad smelling gases or of both.

What I claim is:

l. A method of making semipyrophoric iron from iron oxalate by thermaldecomposition, which method consists in heating iron oxalate in thepresence of indifferent gases maintaining the condition of reaction withrespect to the duration of treatment within limits, above whichpyrophoric and below which normal iron is obtained by the sametreatment. 4

2. Semipyrophoric iron being a black powder and whose ignition-pointin-contact with air is at about C. produced by the method of claim 1.

ALFRED SCHMID.

